Modify and restore NVIDIA control panel settings

Namely:
- Power profile for sunshine.exe
- Global OpenGL/Vulkan DXGI swapchain

src/platform/windows/nvprefs/undo_data.cpp

@@ -0,0 +1,71 @@
+#include "nvprefs_common.h"
+
+#include "undo_data.h"
+
+namespace {
+
+  const auto opengl_swapchain_our_value_key = "/opengl_swapchain/our_value";
+  const auto opengl_swapchain_undo_value_key = "/opengl_swapchain/undo_value";
+
+}  // namespace
+
+namespace nvprefs {
+
+  void
+  undo_data_t::set_opengl_swapchain(uint32_t our_value, std::optional<uint32_t> undo_value) {
+    data.set_at_pointer(opengl_swapchain_our_value_key, our_value);
+    if (undo_value) {
+      data.set_at_pointer(opengl_swapchain_undo_value_key, *undo_value);
+    }
+    else {
+      data.set_at_pointer(opengl_swapchain_undo_value_key, nullptr);
+    }
+  }
+
+  std::tuple<bool, uint32_t, std::optional<uint32_t>>
+  undo_data_t::get_opengl_swapchain() const {
+    auto get_value = [this](const auto &key) -> std::tuple<bool, std::optional<uint32_t>> {
+      try {
+        auto value = data.at_pointer(key);
+        if (value.is_null()) {
+          return { true, std::nullopt };
+        }
+        else if (value.is_number()) {
+          return { true, value.template to_number<uint32_t>() };
+        }
+      }
+      catch (...) {
+      }
+      error_message(std::string("Couldn't find ") + key + " element");
+      return { false, std::nullopt };
+    };
+
+    auto [our_value_present, our_value] = get_value(opengl_swapchain_our_value_key);
+    auto [undo_value_present, undo_value] = get_value(opengl_swapchain_undo_value_key);
+
+    if (!our_value_present || !undo_value_present || !our_value) {
+      return { false, 0, std::nullopt };
+    }
+
+    return { true, *our_value, undo_value };
+  }
+
+  std::string
+  undo_data_t::write() const {
+    return boost::json::serialize(data);
+  }
+
+  void
+  undo_data_t::read(const std::vector<char> &buffer) {
+    data = boost::json::parse(std::string_view(buffer.data(), buffer.size()));
+  }
+
+  void
+  undo_data_t::merge(const undo_data_t &newer_data) {
+    auto [opengl_swapchain_saved, opengl_swapchain_our_value, opengl_swapchain_undo_value] = newer_data.get_opengl_swapchain();
+    if (opengl_swapchain_saved) {
+      set_opengl_swapchain(opengl_swapchain_our_value, opengl_swapchain_undo_value);
+    }
+  }
+
+}  // namespace nvprefs